[wts]

Hello,

I'm new to alcohol injection and am having some difficulty understanding the following quotes taken from this site --> Tuning the LET

Complete combustion (stoich) for gas is about 14.7 A/F. For methanol it is about 6.3. Methanol has less fuel energy than gas, but adds considerable quantities of oxygen. Adding, 10% methanol, to gas creates a new unknown stoich value somewhere in between, maybe closer to about 13.8...who knows?

I say its not some unknown value - its .93 lambda.

A sensor calibrated for gas will read leaner once significant alcohol is injected (more oxygen is available). The issue is calibration. "How do you know exactly what the A/F accuracy is with this new fuel mix?" Unfortunately, you don't.

I disagree. O2 sensors arent "calibrated" for any particular fuel. They measure oxygen content.

It gets even more complex when using a rising rate of alcohol injection. My SMC hardware starts at about 6 psi boost with 70 psi injection line pressure, and ramps up to 100 psi by 16 psi boost. So, now you have not only a new fuel mix, it is also changing. Trying to tune using conventional wisdom with target A/F values is a bucket of worms that may have no practical solution.

What?

According to my admittedly small knowledge of WB controllers, they dont need to be programmed for Lamba because thats what they use. Just tune to 14.7 or 12.0 or whatever your target is regardless of fuel type mix ratio. Right?


If .84 lamba is .84 lamba regardless of fuel mix and my LC-1 is using lambda and converting it to something I understand and displaying a "GAS" AFR of 12.34 then whats the problem?

For instance, if I'm street tuning a turbo application that injecting a 50/50 W/M mix at a rising rate between 1 and 15% of total fuel and the WB displays 1.12 under boost I have to think "is that good or bad?" On the other hand, my reaction time to a display of "16.46" would be instant.

To me its like having to quickly convert Farenheit and Celsius in your head except if you fail to do it quick enough engine damage ensues.

Even if a system is converted to run on 100% alcohol, wouldnt using "GAS" AFR's still make sense if I'm more comfortable using an average of averages such as AFR?


Thanks!

[Rocket468]

Sorry I just now noticed this post. Meth will provide a differnt o2 value on your wideband. Its going to register leaner when properly tuned. Most people will never notces this with alcohol injection because of the small amount being injected. Cars that switch from gas to meth will.

I will add more to this tonight, saw this before heading out the door.

[wts]

I'm interested in the effect alcohol injection has on a WB in a F.I. application. According to my LC1, a 50/50 water/methanol mix enriches the AFR display by .5 from 12.5 to 12.0 when its injected at a rate of no more than 10-15% mix to gasoline by volume.

But the other points that LET site makes are counter to my web research and the vast experience I've gotten turbocharging one engine.
So, yea. I dont know everything.

Thanks!

[candymanjl]

a wideband won't be "tuned" for the fuel you're using but for it to display the correct lambda or stoich it needs to know what fuel you're using. my innvate wideband lets you tell it what fuel type you're using so it'll display correctly. as far as the effects of alchohol on your sensor I peronally haven't heard of any, but you'd have to check with the company that makes your wideband.

[pacemkr86]

well this is what works for me.
I tune my car for the A/F i want.. with the alcohol off

The i tune it till all the "knock counts / knock retard" is gone.

I use the alcohol to supress detenation

[wts]

Now thats an approach even I can understand!

What about this syllogism?

Water is to detonation suppression as alcohol is to power generation.

[pacemkr86]

sounds good to me